Cell type specification remains an unsolved problem in developmental biology. The approach we have undertaken is to study vertebrate homologs of Drosophila genes which are known to be involved in similar developmental processes. My preliminary data have shown that the vertebrate Notch gene is involved in multiple aspects of retinal cell development. To further investigate the role of Notch in these cell fate specification events, I propose to study a number of genes that are now known to be in the Notch pathway. I will first establish the spatial and temporal expression pattern of these genes in the developing retina. Subsequently, I will investigate the functions of these genes by either overexpression or "loss of function" experiments. Along doing this, we also hope to establish a general molecular approach for studying biological functions of genes of interest in the development of vertebrate central nervous system.